As a static mixing device for mixing fluid, a Kenics-type static mixer or the like is widely used. Since this type of static mixer generally does not include a movable component, the static mixing device is widely used in fields, such as the chemical industry and the food industry, in which fluid is required to be mixed in piping. On the other hand, as a dynamic mixing device, a product is widely used that places an agitation impeller in fluid within a mixing vessel and that rotates the agitation blade to mix the fluid.
Patent document 1 discloses an example of a static fluid mixing device. This fluid mixing device is provided with a distribution port in the middle, and is composed of a plurality of fluid guide units obtained by concentrically stacking two discs, that is, one large disc and one small disc formed by arranging in one surface a large number of polygonal-shaped compartments whose front surfaces are open, in the form of honeycomb. The compartments of the large diameter disc and the compartments of the small diameter disc are arranged in different positions such that each compartment communicates with a plurality of compartments opposite it, and these fluid guide units are stacked.
In the fluid mixing device, when the fluid moves through the compartments in the fluid guide units, the fluid is mixed by being dispersed, reversed and combined, and is further mixed by eddying flow, turbulent flow, collision and the like produced in each compartment. The fluid mixing device is characterized in that significant mixing effects are obtained by alternately dispersing and concentrating the fluid in a radial direction, that is, from the center of the fluid guide unit to the outside or from the outside to the center.
However, since, in the fluid mixing device, the area of a fluid flow passage is composed of the areas of only parts through which the compartments of the two discs, the large and small discs, communicate with each other, the mixing effects are limited. As the flow rate of the fluid is increased, the pressure drop produced in the entire device is increased; thus, it is disadvantageously necessary to use a large amount of power.
Since the residues of the fluid and foreign matter are adhered to dead spaces in the compartments, a washing operation for maintenance is time-consuming.
On the other hand, in order to mix liquid within a mixing vessel, a turbine blade or the like is widely used; patent document 2 discloses an agitation blade to increase the efficiency of mixing. In the agitation blade, on both surfaces of a supporting member fitted to an agitation shaft, four pairs of two partially agitating units are fitted, each pair of two partially agitating units being aligned with respect to the rotational plane on each surface; as the outside openings of the partially agitating units of those pairs are positioned further backward with respect to the rotational direction, they are sequentially positioned further backward toward the inside. Consequently, a large degree of mixing is easily and reliably acquired in a short period of time even with a small amount of power.
However, in the agitation blade described above, the fluid is mixed only in the areas around the partially agitating units fitted to the supporting member, and the efficiency of mixing is therefore limited.
In order to mix fluid within a reaction device or a reactor to produce reaction, for example, a methanol synthesis reactor is provided that involves a heterogeneous exothermic reaction. In the reactor, raw gas is reacted with a catalyst, catalyst layers are divided into several parts so that the amount of catalyst put into the reactor is reduced, the gas entering the catalyst layers is cooled and the concentration of a reaction product within the gas is reduced, with the result that the reaction rate in the catalyst layers is increased. Specifically, the outgoing gas in the catalyst layers whose temperature is high due to the exothermic reaction is mixed with the raw gas whose temperature is low and thus the temperature of the outgoing gas and the concentration of methanol, that is, the reaction product are reduced, and they are fed to downstream catalyst layers. In this way, it is possible to increase the reaction speed and the reaction rate in the catalyst layers and thus reduce the total amount of catalyst put into the reactor.
Patent document 3 discloses an example of such a mixing device and a reactor in which gas flows having different temperatures are mixed within a heterogeneous exothermic synthesis reactor. The mixing device is provided within the reactor; the mixing device mixes a high-temperature gas flow from an annular space formed by a partition that is placed parallel to a side wall of the reactor supporting catalyst layers and in a lower part of the bottom of a catalyst bed with a cooling gas flow supplied from an annular pierced supply portion placed in a lower part of the partition under predetermined conditions. In this way, it is possible to optimally mix gas flows having different temperatures and thus improve an inversion rate within the reactor.
However, when mixing is performed by the mixing device, since the cooling gas flow is locally injected into the high-temperature gas flow through the pierced supply portion placed in the annular space, the gases are insufficiently mixed around the pierced supply portion. Hence, in order to sufficiently mix the gases as a whole, a predetermined space is further required. Therefore, a deflector is provided to improve the mixing effects but the mixing effects are limited. Moreover, when an operation is performed with a small amount of gas flow supplied to the reactor and a light load thus imposed on the reactor, since the speed of the cooling gas flow supplied through the holes in the pierced supply portion is reduced, the effects of mixture with the high-temperature gas flow are disadvantageously further reduced. Furthermore, the pierced supply portion for supplying the cooling gas flow is placed in the annular space, and it therefore becomes difficult to produce the annular space as the size of the reactor is increased.